<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
       <input type="text" v-model="msg">
       <div>
           {{msg}}
       </div>
    </div>
    <div id="box">
        <input type="text" id="txt">
    </div>
    <script src="./vue.js"></script>
    <script>
        let vm = new Vue({
            el:"#app",
            data:{
               msg:"a"
            }
           
        })

       /*  var msg = "原生的msg";
        var txt = document.querySelector("#txt");
        txt.value = msg;
        txt.oninput = function(){
            msg = this.value;
        } */
    </script>
</body>
</html>